The robotic garden tools, for example, but not limited to, robotic lawnmowers are extensively used for lawn maintenance activities. Typically, a robotic lawnmower is an autonomous robotic tool and uses battery as a power source. Based on the operating load and duration, there is a need to recharge the battery of the robotic lawnmower periodically. As an autonomous robotic lawnmower work unattended, it is required to find a path to a charging station in case the battery power level falls below a threshold power level during operation.
There are many techniques which are currently used to guide the robotic lawnmower back to the charging station. Firstly, an antenna built on the charging station may be used to navigate the robotic lawnmower to the charging station. However, the antenna may have a limited range in a vicinity of the charging station and thus, there is a possibility that the robotic lawnmower may randomly navigate until it comes close to the charging station. Alternatively, the robotic lawnmower may follow a guide wire that may be used to navigate the robotic lawnmower to the charging station. The guide wire may be a perimeter delimiter or a through wire in the lawn intended to guide the robotic lawnmower and the robotic lawnmower is provided one or more sensors to sense the intensity of a magnetic field generated by the guide wire. However, the robotic lawnmower may follow a same path each time and this may result in undesirable permanent visible tracks and/or makings on the lawn.
To overcome the above mentioned disadvantages, robotic lawnmowers are programmed to follow the guide wire at a distance. This distance is randomly selected each time the robotic lawnmower navigates to the charging station. The robotic lawnmower follows fixed magnetic field intensity while traveling back to the charging station. The fixed magnetic field intensity is randomly selected from one cycle to another. Thus, the robotic lawnmower takes a different path each time it goes to the charging station. This approach effectively addresses the problem of visible tracks on the lawn. However, this approach does not work properly in narrow passages within the lawn. For example, if the randomly selected magnetic field intensity by the robotic lawnmower is small the robotic lawnmower may find it difficult to navigate through the narrow passages.
Also the magnetic field intensity may depend on a variety of factors which might vary dynamically. Such factors may include current in the guide wire, presence of external magnetic objects, change in temperature of electronic components of the garden tool and tolerances of sensor electronics of the robotic lawnmower.
Thus there is a need for an improved system and method to navigate a robotic lawnmower to the charging station.